Practise IB Biology HL A2.1 with evidence-led questions on early-Earth chemistry, protocells, RNA as an early genetic material and radiometric dating.
The synthesis of complex organic molecules in sea water is believed to be an important step in the evolution of life on Earth. Researchers investigated whether the evaporation of sea water containing amino acids could catalyse the formation of dipeptides such as divaline (valine-valine) under prebiotic Earth conditions. They placed different amino acid combinations in a chamber to simulate the evaporation cycles between high tides in shallow seas. In one investigation the amino acid valine was used as the substrate and the percentage yield of divaline was measured after different numbers of evaporation cycles. The experiment was repeated without a catalyst and with either glycine or histidine as catalysts.
This investigation was performed in a chamber at leading to total evaporation of the salt water within one day. The atmosphere inside the chamber consisted of nitrogen, carbon dioxide and water vapour. Evaluate the experiment on the basis of similarity with conditions that existed on the prebiotic Earth.
Outline other possible locations where conditions could have allowed the synthesis of organic molecules under prebiotic conditions.
The Miller-Urey experiment carried out in 1952 tested the hypothesis of the chemical origin of life. What were the key findings?
Living cells could be produced from a mixture of chemicals.
Complex organic molecules could form under simulated primordial conditions.
Life could spontaneously emerge without external influence.
DNA and RNA could self-replicate in a prebiotic environment.
State the name for primitive, phospholipid-enclosed structures that may have preceded cells.